Batteries, which generate electrical energy by way of electrochemical oxidation and reduction, are used over a wide range of applications. For example, the batteries are used in gradually expanding fields, including: devices carried around in user's hands, such as portable phones, laptop computers, digital cameras, video camera, tablet computers, electrically-driven tools, and so on; electrically-driven apparatus such as electric bicycles, electric auto-bicycles, electric vehicles, hybrid vehicles, electric boats, electric airplanes, and so on; power storage apparatus for use in storing electricity generated from renewable energy or surplus generated electricity; or uninterruptable power supply to stably supply electricity to a variety of information communication devices including server computer, base station for communication, and so on.
The battery includes three basic elements which are: a negative electrode containing a material that undergoes oxidation and releases electrons during discharging; a positive electrode containing a material that undergoes reduction and accepts electrons during discharging; and an electrolyte that allows migration of operating ions between the negative electrode and the positive electrode.
The battery can be categorized into a primary battery which is not reusable once it is discharged, and a secondary battery which has at least partially reversible electrochemical reaction, thus are repetitively chargeable and dischargeable.
For the secondary battery, lead-acid battery, nickel-cadmium battery, nickel-zinc battery, nickel-iron battery, silver oxide battery, nickel metal hydride battery, zinc-manganese oxide battery, zinc-bromide battery, metal-air battery, lithium secondary battery, and so on, are known. Among these, the lithium secondary battery is attracting greatest commercial attentions, in view of its relatively higher energy density, higher battery voltage and longer storage life than the other secondary batteries.
Concerning the lithium secondary battery, materials used for positive electrode material and negative electrode material have critical influence on the performance of the secondary battery. Accordingly, a variety of efforts are being made to provide the positive electrode material and the negative electrode material which have stability at high temperature, and can provide high energy capacity and low manufacture cost.